Here is a list of the most common causes of chimney leaks:
No chimney cap or cover: A chimney with no cap or cover allows rain or snow to enter and collect in the firebox. It also gives animals and birds opportunities to build nests, creating blockages in your chimney.
Cracks in the chimney crown: A chimney crown keeps water from damaging the mortar in the bricks and seals the gap between the liner and the outside chimney. Cracks can cause water to gather between the chimney and the flue lining, damaging ceilings and walls.
Faulty chimney liner: If your chimney liner is faulty or has not been installed properly, flue gasses will condensate and lead to chimney fires and moisture build-up in the flue system.
Inadequate chimney flashing: Chimney flashing is a sheet metal installed to create a seal between the chimney and the roof. Damaged or poorly installed chimney flashing can cause serious structural damage.
Deteriorating mortar: Ageing can cause mortar to weaken and moisture to enter through the cracks and crevices. In the winter, water in the cracks can freeze and thaw over time, causing your chimney to lean or collapse.